Electric Eel was basically the same as the Kiss of Mud, except that instead of barbed wire, there were electrified cables dangling above the trench of slop. I leapt in, and for a while it went fine. Halfway through, I started getting cocky. Is this it? Maybe I'm immune to electricity! Then a shock hit my leg and I yelled: "OH SHIT!" I didn't intend to yell that. The words just flew out of my face. As the fear mounted and the people around me churned the mud into a turbulent human gazpacho, I thought, I do not belong here. These people are not like me. They are strong, prepared. I can't do this.

But I had to. I had eleven miles of sloppy terrain to cover, with a fat, stupid paycheck waiting for me at the end.

Back in April, Zeus Jones, an ad agency contracted by General Mills, e-mailed me to ask if I was interested in writing "sponsored content" for Wheaties. The assignment consisted of training for a Tough Mudder and blogging about the experience. For those unfamiliar with it, a Tough Mudder is an event designed by personnel from the British Special Forces. It's a ten-to-twelve-mile obstacle course featuring ice-cold water, adult-sized monkey bars, fire, and electrocution. Zeus Jones told me I was an ideal candidate for such an ordeal, due to my nontraditional athlete's physique and modest following on Twitter.

The job presented an interesting conflict for me as a writer. Lots of athletes receive compensation to endorse sports-related products. I, on the other hand, became an athlete solely for the purpose of promoting a cereal. Both General Mills and Zeus Jones encouraged me to be honest about my experience training (and eating Wheaties). I was even allowed to disclose that I was interacting with/thinking about/writing about Wheaties only because I was being given money to do so. But that's kind of like having parents who smoke pot. Sanctioned subversion isn't subversion; it's branding. I was torn.

Then I figured out how much I owed in 2012 taxes and signed the deal.

For the first time in years, I embarked on something you might call a "fitness regimen," as opposed to a "slow-motion plummet into terminal disrepair." I started running six days a week. At first, I could barely manage a choppy, sweaty mile or two. I hustled a half mile and then walked a half mile. It was the fitness equivalent of the loud-quiet-loud dynamic of a Pixies song. I hated it. Every footfall filled me with resentment for my assignment. Each stride away from my Manhattan apartment and down the lumpy sidewalks along Riverside Drive meant an additional step I'd have to take on my way back. My legs burned and my chest ached. I seethed with envy every time an actual athlete chugged by me like a Terminator. One day I planned to run two miles south, turn around, and drag myself the two miles back home. Instead, I ran the initial two miles, stopped for a slice of pizza, then decided I was still hungry and ate frozen yogurt, too. On the train home, I realized that from a caloric standpoint, I would have been better off if I hadn't left my apartment at all.

Nevertheless, I stuck with it, giving myself only one day off every week. Within ten days I could feel myself rounding (or flattening?) into shape. I still ran at the speed you pretend is running while crossing the street in front of a car, but I could do it for much longer. First a mile at a time without a break for walking. Then one and a quarter. The respites I granted myself in between high-intensity runs grew shorter. After three weeks I could run three miles at a stretch. I moved slowly but steadily, sweating profusely from my back like the oldest guy on a pickup basketball court. I didn't love running, but it was good to know I could do it if necessary.

I also spent the lead-up to my Tough Mudder eating more healthy food. I don't mean I completely abstained from pizza, but I supplemented my regular intake of unqualified garbage with salads, juices, and, of course, Wheaties. I hadn't had the cereal since childhood. Oh, I thought as I lifted the first spoonful to my lips, this tastes…healthy. I have a pathologically low tolerance for soggy cereal, but the coarse, rigid texture of the Wheaties demanded moistening. My technique became to douse my cereal with milk and then devour it as quickly as possible before it passed my mush threshold. My body felt better when I ate Wheaties instead of, say, a doughnut for breakfast. Except the mouth part of my body. I contemplated mixing one part cereal with one part chocolate chips, or using coffee instead of milk. I resisted, if only because at the end of that road sat a breakfast ice cream sundae dusted with crumbled Wheaties—also known as Rock Bottom.

Two days before the event, I flew to Chicago, where I met Ned, the other Wheaties sponsoree, for the first time. The Mudder, I had been told, was a collaborative experience. Several obstacles could be surmounted only with help. Ned was my help. I was his. I really, really hoped we got along.

Fortunately, we became fast friends. Ned was born in the U.K., and his voice has a Britishy twinge to it, which he told me grows stronger when he's drunk. He's funny and charming and says things like "cheers!" (to mean goodbye) without sounding like an ass. Ned and I stand at roughly the same height, but he possesses a little more thickness. He's not what you'd call "shredded" (even if you were the kind of guy who used that word), but he's definitely solid. Over the course of our weekend together, our size difference manifested itself as a number of classic bigger-guy/smaller-guy dynamics. The strength of Samwise paired with the frailty of Frodo. Shrek's grumpiness contrasted against Donkey's pep. And, on occasion, Lenny's dreamy escapism versus George's Dust Bowl grit.

"This is bonkers, right?" Ned said as he settled into my rented Hyundai.

"Oh yeah, totally bananas. I'm right here with you."

"Good."

We drove from Chicago to Sandwich, Illinois, together, and said our hellos to the Zeus Jones team and the production crew that would film our performance. This seemed like torture—there's a reason you don't make a sex tape the night you lose your virginity—but rules are rules.

The morning of our reckoning, Ned and I awoke early and decided not to shower. Why bother? As the hotel had not yet splayed out the bounty of its continental breakfast, we made a run to the local Dunkin' Donuts to obtain breadlike provisions for ourselves and to procure doughnuts with which to bribe the production team into portraying us favorably on video. I ate a bagel, and then, in a moment of weakness, a doughnut. Then, in a moment of strength, I resisted eating a second doughnut. My first victory of the day.

The advertising people, the production team, Ned, and I piled into our rental car caravan and made the trek to the Mudder site, twenty miles away. Each of the many sponsors had its own booth. Mudders (which is the name of the competitors as well as the race itself) of various shapes, sizes, ages, genders, and races goofed off with their families or got psyched for the run. The day was hot by nine and getting hotter. I applied sunscreen, taking special care with the parts of my forehead that have gradually appeared as my twenties march toward my thirties.

We had to scale a six-foot wooden wall just to get to the starting line. Great, I thought as I wriggled over. I'm barely in good-enough shape to begin this race, never mind finish it. While the base camp contained an encouraging mélange of body types, our wave of Mudders seemed uniformly sinewy. I noted the resolve in the eyes of those around me, as well as several "because I can" beards that military personnel tend to grow when they are on extended leave. Panic flooded my body as I realized that maybe this was not going to go well. I should have trained better. Harder, longer runs. More push-ups. Fewer cupcakes.

A fit black guy named Sean appeared to bring the hyped-up crowd to a bloodthirsty level of hype-itude. He invoked the Wounded Warrior Project, with which the Tough Mudder is entwined. He encouraged us to shake hands with our fellow Mudders and reminded us that the challenge isn't to get the best course time, but rather to make sure everyone around you progresses safely through the course. I tried to get psyched up adding my own shaky "hooRAH!" to the chorus, a little self-conscious about never having served in the armed forces. I began to feel solidarity with the frenzied throng of athletes around me. We all sang the national anthem. I stood at the beginning of an eleven-mile journey full of twenty-two plotted obstacles and myriad other potentially humiliating difficulties. I didn't know exactly what to expect, except that it was going to suck.

"Let's do this!" I cried, slapping Ned on the shoulder as we were released onto the course. He didn't hear me.

We started at the head of the pack, but on the quarter-mile run up to the first challenge, an unending stream of well-muscled, athletic Mudders surged past us. We'd already fallen behind a significant portion of the competitors on our gently paced jog toward Obstacle 1: the "Arctic Enema." (Now is as a good time as any to mention that all the obstacles have super-macho, and often penetrative, names.) The Arctic Enema involves jumping into a pool of filthy freezing ice water. Once you're in up to your chest, you have to duck under a submerged wooden barrier and swim to the other side. As soon as I plunged my head below the surface of the frigid tub of muck, I realized I had sucked very little oxygen into my body. I worried my Mudder was going to end there, on the first obstacle, with a gaping mouth and lungs full of water and MRSA. Unfortunately, on the way out of the pool, I smacked my shin, cutting it open under my sock. I didn't see any blood, but I have a kind of supernatural intuition for when I'm bleeding. It wasn't exactly a promising start to the event. But, I'd survived, and so I continued.

The second obstacle, "Kiss of Mud," consisted of a thirtyish-foot crawl under barbed wire across a patch of watery goop. The crawling had caused me a lot of anxiety leading up to the event. I don't suffer from any clinical level of claustrophobia, but I do have a mild fear of getting stuck in a muddy tube the width of an elephant's anus while a former Marine yells at me. Fortunately, even scrunched up like an inchworm, my back never scraped the barbed wire. My forearms propelled me through the silt below. I felt good (if muddy and still bleeding) as I stood back up. I can do this, maybe, I thought.

Team Wheaties trundled through the "Electric Eel", mentioned above, and on to "Walk the Plank." The latter obstacle involved of a climb up a twenty-foot ladder and a leap into (yes) muddy water. Fact about me: I love jumping over/into things. This was a blast. It was the first time on the course when it occurred to me that the Tough Mudder is a thing people do for fun. That simple, moronic realization turned my whole day around. I stopped viewing my task as one of survival and started thinking of it as (gasp) recreation.

The eighth challenge, the "Warrior Carry," forced Ned and me to step up our leisurely pace. We each had to carry the other for a hundred-yard stretch of the course. The interview we did with the production team afterward was my favorite moment of the day (incidentally, it didn't make the final cut of the promo video). Ned and I looked straight into the camera and deadpanned:

"This event started off really easy when Ned was carrying me, but somewhere around the time I had to start carrying him, it got way harder."

"I had the opposite experience. I thought it started off hard and then got radically easier around the midpoint."

"I guess we're just different kinds of champions."

We plodded onward from there without incident until we hit the eleventh hurdle, "Hangin' Tough," in which Mudders had to swing from a series of rings across, you guessed it, a muddy puddle. As I had done almost no strength training, any events relying on the upper body were going to be very nearly impossible. I made it two rings before my splashdown. Ned got almost the whole way across. Then Dom from the production team told us he didn't get the shot he needed, so we had to go back and fail again for the benefit of the cameras.

"Oh, no. Come on," Ned said.

"Let's go," Dominic replied. So we did.

The thing they don't tell you about a Tough Mudder is that for all the adrenaline pumping and barbed-wire-bicep-tattoo sporting, a lot of the day is fairly idyllic and contemplative. I hadn't spent so much time jogging through the woods in years—or ever. Ned and I had time to chat about plans for the future. Our Of Mice and Men moment consisted of Ned dreamily recounting his plans for his cereal earnings while I urged us onward.

"I'm going to eat tacos tonight. And I'm going to get a bulldog with this money," he said, with a faraway look in his eyes.

The "Mud Mile" was really only a football field's worth of sloppy hillocks. The challengers had worn paths through the glop, but I decided to scale the mounds' full heights. In a life of taking the easy way out of physical exertion, it was the first time I had ever intentionally made things more challenging for myself. It felt like a milestone.

Of all the course's challenges, "Everest," the second to last, best exemplified the Tough Mudder spirit that Sean had laid out at the beginning of the day. The obstacle consisted of a skateboard quarter pipe, greased down for difficulty of scaling. After almost eleven miles of course, few had the lower-body strength to rocket up the pipe's curve and the upper-body power to haul themselves onto the deck above. So, in the interest of camaraderie, several folks who had already finished already came back to hoist less-evolved bodies over the top. It made me feel happy and part of a nice community of people interested in one another's success. Two ripped dudes grabbed my forearms.

"Get your leg over," said one dude.

"I can't!"

"Yes you can!" he commanded. With a grunt, the two men pulled me over the lip. I vowed to take at least a month off from making fun of guys with tribal tattoos.

"That's going to look great on the video," Joel the cameraman grinned. Great.

Just a few yards past Everest, I faced down the Mudder's final obstacle: "Electroshock Therapy", a fifty-foot sprint through water over bales of hay amid a jungle of electrified wires. As I'd approached other obstacles, I'd stood in lines of people waiting their turn and clusters of competitors strategizing how to best go about a given challenge. This event marked the only time a swarm of Mudders stood congregated out of good old-fashioned fear. Ned opted out. I was given the option to bypass the obstacle as well, but there was no way I was going to wimp out with the Challenge's finish line in sight.

In front of me stood Sean, barking encouragement. Individual Mudders ran through the dense web of electricity. Some powered across without faltering, while others bellowed in anguish and crumpled into the water. Several groups marched through the danger as a team, arms locked in solidarity, dragging their compatriots whom the voltage had felled.

I took off running with my arms braced in front of my face to protect my eyes, which I assumed were especially vulnerable to electrocution. At first I felt nothing. Then the shocks started to hit, stinging my arms like thorns. In the middle of my first shock, I thought: Why are people falling? This isn't so bad. Then I felt the real difficulty of the obstacle. The current grounded itself through my body when my feet met earth. It felt like when you miscalculate the end of a staircase and the floor slams up against your heel unexpectedly. With every step. I continued to run. My knees buckled, but I stayed upright. Triumphant, I searched for Ned on the other side. He had been ushered across the finish line without me. Goddammit.

Ned circled back, and we ran across the finish line together. I clenched my fists and yelled, "Anythiiiiiing is possibllllle!" as a tribute to Kevin Garnett's postgame interview after the Celtics won the 2008 NBA title.

In a poetically disappointing turn, Dom told us he hadn't gotten the shot, and he made us run through again. We barreled across the finish line once more, after which we posed for a photo with another team of Mudders and received bright orange sweatbands as trophies for completing the course. I texted my parents and girlfriend to announce that after four hours of this, I was still alive.

The event that had dominated the past month of my life (training, blogging, worrying) was finally concluded, and I felt good but empty. What next? When Wheaties posted the promotional video on YouTube, I got tons of congratulatory messages from friends and family, but I was already two weeks removed from the experience itself. I was more impressed with how expertly the video crew cut the footage together into a cohesive story than I was with my own exploits.

I realized that after a month of fearing and resenting "those guys" who did "stuff like that," I had become one myself. And it just seemed regular. I didn't feel impressive. Maybe I had become a fitness dude. I had enjoyed the Tough Mudder enough that I considered (and am still considering) signing up for the New Jersey Mudder in October. As the video draws to a close, I say that I feel changed, like a better version of myself. In the moment, it is an honest sentiment.

Cut to: Last night. My apartment. I'm alone on the couch eating ice cream from the carton. I haven't worked out since the Mudder. Haven't done a single push-up. Haven't run a solitary mile. It seems I spoke too soon about the new, better me. I'd hoped for a feel-good Hollywood ending to write about. Instead, I pulled a Larry David. After a month of diet, exercise, and accomplishment I failed to learn any lesson at all. It's like I'm spiting my own body.

I've probably gained fifteen pounds over the past month, which would be alarming if I hadn't lost fifteen pounds training for the Mudder. I'm back to square one, which in this case is less square and more rounded at the edges. I'm skinny, but a soft skinny. I have strong legs, but my arms are like pea pods with single peas for elbows.

In the run-up to the Mudder, thanks to corporate sponsorship, I was in the best shape of my adult life. Since then, my body has returned to its normal shape, and my brand-new of running shoes (optimistically purchased upon my return home) remain unlaced in their original cardboard box. The corporate sponsorship diet, like any fad fitness program, proved unsustainable.

I still keep my Tough Mudder headband on my desk, and my new shoes are a bright orange. So maybe I have changed after all, but in a more subtle way than I'd hoped.

Sure, I may not be the kind of guy who works out every day for the pure enjoyment of it.